Iowa among states prohibiting contact of copper, foods with pH below 6

Friday, 11 August, 2017, 08 : 00 AM [IST]

A number of American states, including Iowa, have adopted the United States Food and Drug Administration’s (FDA) Model Food Code, which prohibits copper from coming into direct contact with foods whose pH is below six. Examples of these are vinegar, fruit juice and wine.

Licensees and permittees selling and serving alcoholic beverages in copper mugs have been directed to adhere to the applicable federal guidance and state regulations regarding the use of copper and copper alloys in contact with food and beverages.

The pH of a traditional Moscow Mule - an alcoholic cocktail, usually served in a copper mug - is well below 6.0. This means that copper mugs that have a copper interior may not be used with this beverage.

However, copper mugs lined on the interior with another metal, such as nickel or stainless steel, are not only permitted to be used, but are also widely available.

The recent popularity of Moscow Mules has led to inquiries regarding the safe use of copper mugs and this beverage. The use of copper and copper alloys as a food contact surface is limited in Iowa.

Applicable laws/rules/regulations4-101.14 Copper, use limitation(A) Except as specified in paragraph (B) of this section, copper and copper alloys, such as brass, may not be used in contact with a food that has a pH below six, such as vinegar, fruit juice or wine, or for a fitting or tubing installed between a backflow prevention device and a carbonator.

(B) Copper and copper alloys may be used in contact with beer brewing ingredients that have a pH below six in the pre-fermentation and fermentation steps of a beer brewing operation, such as a brewpub or microbrewery.Public health reasoningHigh concentrations of copper are poisonous and have caused food-borne illnesses. When copper and copper alloy surfaces contact acidic foods, copper may be leached into the food.

Carbon dioxide may be released into a water supply because of an ineffective or non-existent backflow prevention device between a carbonator and copper plumbing components.

The acid that results from mixing water and carbon dioxide leaches copper from the plumbing components, and the leachate is then transferred to beverages, causing copper poisoning.

Backflow prevention devices constructed of copper and copper alloys can cause, and have resulted in, the leaching of both copper and lead into carbonated beverages.

Brass is an alloy of copper and zinc, and contains lead, which is used to combine the two elements.

Historically, brass has been used for items, such as pumps, pipe fitting, and goblets.

All three constituents are subject to leaching when they contact acidic foods, and food poisoning has resulted from such contact.

The steps in beer brewing include malting, mashing, fermentation, separation of the alcoholic beverage from the mash and rectification.

During mashing, it is essential to lower the pH from its normal 5.8 in order to optimise enzymatic activity.

The pH is commonly lowered to 5.1-5.2, but may be adjusted to as low as 3.2.

The soluble extract of the mash (wort) is boiled with hops for a period ranging between one and 22 hours, or more.

After boiling, the wort is cooled, inoculated with brewer’s yeast and fermented.

The use of copper equipment during the pre-fermentation and fermentation steps typically result in some leaching of copper.

Because copper is an essential nutrient for yeast growth, low levels of copper are metabolised by the yeast during fermentation.

However, studies have shown that copper levels above 0.2mg/L are toxic or lethal to the yeast.

In addition, copper levels as low as 3.5 mg/L have been reported to cause symptoms of copper poisoning in humans.

Therefore, the levels of copper necessary for successful beer fermentation (i e below 0.2mg/L) do not reach a level that would be toxic to humans.